The present invention relates to improvements in or relating to a sialon base ceramic material which can be applied to cutting tools or wear-resistant tools.
Sialon is generally classified into beta-sialon that is obtained by adding Al.sub.2 O.sub.3, AlN, SiO.sub.2, etc. to Si.sub.3 N.sub.4, followed by heating to form a solid-solution thereof, and is expressed in terms of the general formula Si.sub.6-z Al.sub.z O.sub.z N.sub.3-z wherein 0&lt;z.ltoreq.4.3, and alpha-sialon that has a metal element M occupied as a solid-solution in its lattice, and is expressed in terms of the general formula M.sub.x (Si,Al).sub.12 (O,N).sub.16 where 0&lt;x.ltoreq.2. The former beta-sialon possesses high toughness but low hardness, whereas the latter alpha-sialon possesses relatively low toughness but high hardness.
Of these two types of sialon, various attempts have been made to make effective use of beta-sialon as tool materials, because of its high toughness. Not until now, however, have there been known any substantial attempts to use alpha-sialon as a tool material.